This invention relates to plastic draw tape bags, and more particularly, to an improved draw tape and method of manufacture.
Bags made of thin polyethylene material have been used in various sizes. Small bags are used in the packaging of sandwiches and the like; larger bags are used as shopping bags; and even larger bags are used for containing trash.
A particularly advantageous closure for such a bag includes a draw tape constructed from the same polyethylene material. U.S. Pat. No. 3,029,853--Piazzi, and British Pat. No. 1,125,363--Jortikka are examples of draw tape bags. Such closures have been successively employed on these bags.
Draw tape closures for large trash bags, and the manufacture of these draw tape trash bags, are described in the related applications identified below.
In such bags, the tape is preferably unoriented polyethylene which is heat sealed to the opposing panels of the bag at the sides thereof. The weakest part of the draw tape is at the heat seal. This weak point should be located at the point of lowest tensile load, which is furthest from where the user pulls the tape. For this reason, the tape is normally in a hem with a notch at the center of the bag, so that the user grasps the tape at a point furthest from the heat seal.
Economy of manufacture is one of the prime considerations in these bags. The cost of the draw tape is a significant part of the total bag cost, so that any economies in draw tape cost advantageously reduce the ultimate cost of the bag.
It is an object of the present invention to reduce the cost of the draw tape in a trash bag by significantly stretching the tape prior to insertion into the bag.
It is another object of the present invention to use stretched, oriented, polyethylene tape in a draw tape bag without significantly weakening the heat seal where the tape is secured to the sides of the bag.